The present invention relates to a mounting arrangement for mounting and attaching a gas turbine engine to an aircraft pylon structure and aircraft.
Ducted fan gas turbine engines for powering an aircraft are mounted upon and suspended from the aircraft via a pylon structure. The pylon extends from the aircraft wing and a mounting arrangement interconnects the engine to the pylon and so to the aircraft. Once conventional type of mounting arrangement is the so-called core mount, where the pylon extends through the engine nacelle, across the by-pass duct towards the core engine casing. The mounting arrangement then interconnects the core engine casing, and so core engine, to the pylon. Generally both a front or forward mounting in the region of the compressor section of the core engine and a rear mounting in the region of the turbine section of the engine are used to connect the core engine to the pylon at two axially separated locations. The fan casing and nacelle may either be independently connected to the pylon or, more typically are supported from and by the core engine casing and core engine mountings.
The mountings are required to carry and transmit all of the operating loads of the engine including side, vertical axial (thrust) and torque loads.
One current design of core mounting arrangement for attaching the core engine to the pylon comprises an axially extending mounting bracket or beam assembly which is securely bolted to and extends axially from the pylon. The use of an axially extending bracket means that the core engine connection can be axially spaced from the pylon position and permits the axial positions of the front and rear engine mountings from the pylon to be further apart, reducing the bending moment on the engine. The use of such a bracket extending forward is preferable to extending the pylon structure itself further forward. This is because extending the pylon would make assembly and integration of the pylon with the engine problematic. It also has an adverse aerodynamic effect on the airflow through the fan duct. A pin or ball joint extends from the forward end of the mounting beam and engages within a hole in a bracket or boss which is connected to or internal with the core engine casing. The pin transmits and carries the vertical and side loads of the engine and provides the main support of the engine from the pylon and aircraft. At the rear of the mounting beam is a balance beam which extends circumferentially and is connected to mounting beam at the mid point of the balance beam. Either end of the balance beam is connected to thrust links which extend forward and connect to points on either side of the core engine casing. The thrust links and balance beam take the axial loads of the engine, with the loads from each side being balanced by pivoting of the balance beam.
Such an arrangement adequately carries the engine loads under normal operation. However in the unlikely event that the bracket, balance beam or one of the thrust links fails the mounting is no longer able to carry the required engine loads.
In order to overcome this and provide built in redundancy the bracket may be split into two symmetrical left and right halves, referred to as split brackets. Each of the split brackets is arranged to be capable of carrying all of the side and vertical engine loads so that the loads can be carried in the unlikely event of one of the split bracket failing.
In other mounting arrangements it has also been proposed to provide additional links and connections between the pylon and core engine than are strictly required to support the engine in normal use. The idea is to provide a mounting with built in redundancy so that if one link or connection should fail then the loads would be carried by the other links.
A problem with the above arrangement and the split bracket arrangement however is that all of the links and connections, and both of the split brackets are subject to the engine operating loads under normal operation. Consequently they will have all experienced similar stresses and fatigue. It is therefore likely that if one link, split bracket or connection fails then the other links or split bracket may similarly fail. This is even more likely since the other links, split bracket and connections will be carrying an increased load to compensate for the failed link or connection.
It is therefore desirable to provide an improved gas turbine engine mounting arrangement which has improved failure tolerance and/or which offers improvements generally.
According to the present invention there is provided a gas turbine engine mounting arrangement for attaching a gas turbine engine to an aircraft via a pylon, the arrangement comprising a main mounting means and an auxiliary mounting structure, the main mounting means interconnects the engine with the pylon and carries the engine loads under normal operating conditions, and an auxiliary mounting structure is capable of interconnecting the engine with the pylon and is arranged to be substantially unloaded under normal operating conditions; wherein the auxiliary mounting means comprises a safety bracket and an auxiliary interconnecting means, the safety bracket is independent of the main mounting means and is attached to the pylon, auxiliary interconnection means extends from the safety bracket to connect the safety bracket to the engine, the auxiliary interconnection means and the safety bracket only engaging with the engine and carrying substantial engine loads in the event of failure of the main mounting means.
Preferably the main mounting arrangement comprises a main bracket and a main interconnecting means, the main bracket attached to and extending in an axial direction of the engine from the pylon, and the main interconnection means attached to the main bracket to interconnect the main bracket with the engine. Furthermore one of the main interconnection means extending from the main bracket to interconnect with the engine preferably comprises a pin and corresponding socket, the pin engages the socket.
Preferably in one of the main interconnection means extending from the main bracket to interconnect with the engine comprises at least one thrust link, one end of the thrust link is attached to the main bracket with the opposite end of the thrust link attached to the engine, the thrust link extending between and connecting the main bracket and the engine. The auxiliary interconnection means extending from the safety bracket may comprise at least one ear, the at least one ear is connected to the at least one thrust link in order to connect the safety bracket with the engine, the ear connected to the thrust link so that it will only engage with the thrust link in the event of failure of the main mounting. Preferably there is a pair of thrust links, the pair of thrust links is laterally oppositely disposed about and attached to the main bracket. There is a pair of ears, the ears extending from laterally separated points of the safety bracket.
Preferably the safety bracket is interposed and sandwiched between the main bracket and the pylon. The arrangement comprises at least one mounting fastener, the at least one mounting fastener attaches the main bracket to the pylon may also attach the safety bracket to the pylon. Alternatively the safety bracket is attached to and mounted to the pylon independently of the main bracket.
The safety bracket preferably comprises a generally planar member, the generally planar member is attached to the pylon, with the auxiliary interconnection means which extend from the safety bracket connected to mounting points formed on the safety bracket.
Preferably the arrangement comprises a pin and a clearance hole, each of the auxiliary interconnection means which interconnect the safety bracket and the core engine, the safety bracket and engine via a pin mounted within a corresponding clearance hole.
The auxiliary interconnection means extending from the safety bracket may comprise at least one safety link which is pivotally attached to the safety bracket. There may be a pair of safety links. The pair of safety links may be laterally oppositely disposed on and attached to the safety bracket.
Preferably the mounting arrangement comprises a front mount attaching to and connecting a generally forward portion of the engine to the pylon. Furthermore the mounting arrangement preferably connects and attaches to a core engine of a ducted fan gas turbine engine.
According to a second aspect of the present invention there is provided a gas turbine engine mounting arrangement for attaching a gas turbine engine to an aircraft via a pylon, the arrangement comprising a main mounting means and an auxiliary mounting structure, the main mounting means interconnects the engine to the pylon and carries the engine loads under normal operating conditions, and the auxiliary mounting structure is capable of interconnecting the engine with the pylon and is arranged to be substantially unloaded under normal operating conditions; wherein the main mounting means comprises a main bracket, a pair of thrust links, a pin and a corresponding socket, the pair of thrust links disposed laterally on either side of the main bracket, the pin and corresponding socket within which the pin is engaged, is disposed at a distil end of the main bracket, the pin and socket and the thrust links interconnecting the main bracket to the engine, the auxiliary mounting means comprises an independent safety bracket, a pair of safety links, and pair of ears extending from the safety bracket, the safety bracket is connected to the pylon and is disposed between the main bracket and the pylon, the safety links extend between the safety bracket and engine and are pivotally connected to the safety bracket and engine, and the ears are connected to the respective thrust link, the connections between the ears and thrust link and the safety link connections are arranged to connect the engine to the safety bracket via a pin mounted within a clearance hole so that the safety bracket only engages with the engine and carries substantial engine loads in the event of failure of the main mounting means.
According to either aspect of the invention the auxiliary interconnection means and the safety bracket may be arranged in use to engage with the engine and carry partial engine loads in conjunction with the main mounting means under high engine load conditions.